The Monarch class was a class of three coastal defense ships built by Austria-Hungary at the end of the 19th century. The Monarchs were the first ships of their type to utilize turrets. The class comprised three ships: SMS Monarch, SMS Wien, and SMS Budapest, each armed with four 240 mm (9 in) L/40 guns in two turrets and capable of 15.5 knots at full speed. Budapest was fitted with slightly more modern and powerful engines, giving her a top speed of 17.5 knots.

Coastal defence ships were warships built for the purpose of coastal defence, mostly during the period from 1860 to 1920. They were small, often cruiser-sized warships that sacrificed speed and range for armour and armament. They were usually attractive to nations that either could not afford full-sized battleships or could be satisfied by specially designed shallow-draft vessels capable of littoral operations close to their own shores. The Nordic countries and Thailand found them particularly appropriate for their island-dotted coastal waters. Some vessels had limited blue-water capabilities; others operated in rivers.